Belief duplication



Jan. 3, W50 J. .J. HRAUND 2,493,439

RELIEF DUPL I CATION Filed Sept. 24, 1946 2 Sheets-Sheet l ELF Jan. 3,1950 J; BRAUND 2,493,439

RELIEF DUPL ICA'I'ION Filed Sept. 24 1946 2 Sheets-Sheet 2 o o o o m g 9JUhHJQEdUHd Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE RELIEFDUPLICATION John J. Braund, Washington, D. C. Application September 24,1946, Serial No. 698,973

26 Claims.

This invention is directed to duplication of relief and particularly toan improved process and machine which will duplicate relief with a highdegree of accuracy. The invention is particularly adapted to thereproduction of relief maps, where precision is an indispensible factor,but is also adapted to duplication of other reliefs of utilitarian andornamental nature.

The general object of the invention is to produce accurate reliefseconomically, and to provide a relatively simple and rapid process, anda low cost, easy-operated machine for this purpose.

A further object of the invention is to accurately reproduce reliefs inthermoplastic sheet material.

Still another object of the invention is to produce topographical reliefmaps and other profiled objects having indicia correlated with thecontour thereof, and to mold article blanks upon which the indicia havefirst been printed or otherwise inscribed in a manner to secure accurateregistry of the indicia and contour and cause the indicia to maintainthe same positions transversely after deformation of the blank intoprofile as before, and this regardless of whether the contour is ofregular or irregular shape.

A further object of the invention is to secure uniform heating ofthermoplastic sheet material in the production of relief therein so thatall areas will be softened to the same degree for molding purposes.

Still another object of the invention is to produce relief inthermoplastic sheet material employing a single mold, through theapplication of vacuum to the side of the sheet facing the mold whilesubjecting the exposed face of the sheet to uniform heat.

An important additional object of the invention is to mold areas ofdifferent amplitude or elevation of a relief in sheet material inprogressive order, beginning with areas of lower amplitude or elevation,and to accomplish this by controlling and progressively varying theoperating conclitions.

According to my prior Patent No. 2,066,555 granted January 5, 1937,duplicate reliefs are produced by securing a sheet at the edges over aliquid reservoir and deforming the sheet by hot liquid under pressureinto an inverted female mold disposed above the sheet. While suchprocedure has been successful in producing relief with a fair degree ofaccuracy, the machine required has been found to have been morecomplicated than desirable in construction and awkward to operate, alsoless accurate in results when molding either ductile metal orthermoplastic non-metallic sheets. The present invention has all theadvantages of my prior patented machine and is a definite improvementthereon from the standpoint of procedure, simplified machineconstruction, and operation, and duplicating accuracy.

It should be explained preliminarily that the mode of heatingthermoplastic sheet material for the production of relief therein is amatter of considerable importance. The heat should be uniformlydistributed throughout the entire area of a sheet to be molded.Overheating in local areas is likely to result in blisters and warpingand produce a defective product. Underheating of areas is at least asserious since molding operation is likely to cause cracks or rupturesand ruin the sheet.

Again, the heat must be carefully controlled as to temperature. It isvery easy to overheat a plastic sheet beyond the temperaturesappropriate to molding, and also to heat it above its softening pointtoo rapidly. I found the best results are secured by slowly raising thetemperature of a thermoplastic sheet and molding relief areas ofdifferent amplitude at different temperatures, starting with low reliefareas during initial heating and progressively molding areas of higheramplitude, or elevation as the temperature of the sheet increases. Thisis particularly important in producing relief maps, to secure relativelyuniform expansion of the sheet in adjoining areas of different amplitudeso that points of the sheet will be expanded vertically withouthorizontal shifting and remain in accurate registry with correspondingpoints of the mold matrix. This cannot be done if the sheet is too hotand too soft or unevenly heated, since under such conditions areas ofdifferent amplitude of the sheet are likely to mold simultaneously andresult in excessive stretching and thinning of the sheet in one area andlittle or no stretching in an adjoining area. The resulting relief maybe inaccurate, and if indicia are present they will be shifted laterallyrelative to one another and out of correct registry with the relief.

I have found that heat transmission through a dry gas, ordinarily air,is best suited to the production of relief in thermoplastic sheetmaterial. It is within the scope of the invention to employ variousmodes of heating depending upon the nature of the relief and the degreeof precision required. Radiant heat :from a battery of infrared or otherelectric lamps, or electrical resistor heating units has been employedsuccessfully, but this is recommended only for work not requiring a highdegree of perfection. It is difficult to locate the radiant heatingmeans in spaced relation to a blank sheet to be molded and obtainuniform heating through the area of the sheet. Also, the temperature ofthe sheet is likely to be raised too rapidly, it being dinicult toproperly control such type heating means.

It is also possible to locate a closed dead air chamber over one side ofa thermoplastic sheetand provide electric lamps or other heating meansin such chamber in substantially spaced relation to the sheet to secureheating of thesheet by conduction. This mode likewise is recommendedonly where perfect results are not required since it is subject to thesame difficulties as radiant heating above referred to.

I have found that convection. heating is' most satisfactory, and is theonly mode which can be employed successfully where a high degree ofprecision of relief and the absence of flaws are required, as in thecase of relief maps. Circulation of dry steam in a closed chamber overthe face of a thermoplastic sheet can be employed with opaque sheetmaterial, but it is likely to result in clouding of a transparent sheet,from slight condensation of steam on the sheet surface. I, therefore,prefer to circulate dry hot air over the sheet. I find, further, thatbetter control of the heating temperature to gradually raise thetemperature of a sheet may be secured by constantly supplying fresh air,heating it and circulating it over the sheet, and then followin it toescape. If dead hot air is trapped adjacent the face of the sheetcirculation is impeded and the temperature of the sheet is likely to beraised too slowly rather than too rapidly.

According to my new process a female mold is provided with the desiredrelief formed therein. During or after casting of the mold a series ofholes are formed at intervals of a few inches, more or less. Such holeswill communicate with the deepest and other points of all mold cavities,also with flat areas. Hydrostone, a mixture of plaster of Paris andlime, or other suitable durable plaster, with or without the additionofasbestos fibers to give added strength and quicker cooling aftermolding, may be used in formation of the mold.

A flat relatively thin sheet of transparent or opaque thermoplasticmaterial will be employed for the relief. V-inylite or other suitablesynthetic resins which are durable and non-warm ing, and which have arelativelylow softening point somewhat above 100 F. are preferred. Thethermoplastic sheet is preliminarily inscribed for many but not allreliefs, depending on their nature, by

, printing or otherwise with desired indicia. The

blank sheet is then placed on the mold while in hard state and whereindicia are presenttheymust be brought into accurate registry with thecorresponding points of the relief of the mold. The sheet is firmlysecured in sealing contact with a frame surrounding the mold. A very lowpreliminary vacuum is then applied to the mold side of the sheet beforeits temperature has been raised up to the softening point, particularlythe V margins of the sheet beyond the mold, to bring the hard sheet intofirm contact with the margins of the mold and insure against warping.This will frequently produce a slight dishin effect over all moldcavities also. i

the vacuum to insure accuracy of relief.

Following these initial preparations a progres sive molding operation iscarried out. This is accomplished through the simultaneous applicationof vacuum to the mold side of the sheet and heat to the exposed face ofthe sheet. Convection heating by circulating warm air over the sheet ispreferably employed. Heating gradually raises the temperature of thesheet up to and beyond its softening point. The vacuum is also graduallyincreased in stages to cause the sheet to first contact the shallowermolding surface portions of the mold cavities and thereafter graduallybe drawn down into contact with the deepest molding surface portions ofthe mold cavities. In this manner substantially uniform stretching ofthe sheet in areas of different elevation is obtained.

.In this manner, also, registry of the indicia, where present, on thesheet with the corresponding points of the mold cavities is preserved.

When the molding operation has been complet ed, a matter of about twentyminutes, heating is discontinued and the completed sheet is cooled andset, preferably by circulating cool air over the exposed face of thesheet while maintaining Cooling is continued until the sheet and themold are well below the softening point of the sheet, say

to F. or below, also a matter of about twenty or twenty-five minutes.The sheet with the relief permanently set therein is then removed fromthe mold. The process is repeated with succes sive further sheets untilthe desired number of duplicates have been obtained. The entireoperation requires only about three-quarters of an hour for eachduplicate.

The vacuum range and the heating temperature range 'will vary accordingto characteristics of the particular synthetic resins of which thesheets are formed. Unless sheets of substantial thickness are employedor reliefs of unusual complication are to be produced neither'highvacuum or high temperature is required. For example, in the case ofvinylite resin sheets of .015 to .020 inch thickness and. having asoftening point of about F., the vacuum employed in the preliminarystage may be about one inch, fo lowing which a lowheat is applied tobring the temperature up to about 109 F. Thereupon the vacuum may beincreased to about two inches. When the temperature has furtherincreased upto the softening point of he sheet, about 125 the vacuum maybe increased to three inches. When the temperaure has risen to F. thevacuum may be increased to four inches. Heating may be continued to F.as a sufficient maximum. The vacuum then may be again raised to fiveinches, which has been found the maximum necessary to produce accuratereliefs under the process in many but not in all cases. During thesubsequent cooling stage the maximum vacuum is maintained and brokenonly after the molded sheet has set fully.

The invention will be understood by reference to the illustrativeembodiment of my new machine for carrying out my new process shown inthe accompanying drawings and the detailed description following.

In such drawings:

Fig. l is a sectional elevation of a relief duplicating machineaccording to the present invention;

Fig. 2 is a top plan view of the machine shown in Fig. 1;

Fig. 3 is a fragmentary top plan view of a indicia-bearing relief map;and,

Fig. 4 is a fragmentary sectional elevation of a mold with the reliefmap of Fig. 3 therein.

The invention will be described in its application to the duplication ofrelief maps. The original of such a map will preferably be formed ofductilesheet aluminum or copper according to the method of my priorPatent No. 1,866,448, granted July 5, 1932. According thereto such aflat'metal blank is first printed or otherwise inscribed on its rearface with elevation contour lines and elevation and other legends. Suchindicia, likewise land and water areas of different elevation, may beprinted in different colors. The map blank is then firmly secured aroundits margin'and placed with its top face down upon a compressible pad andembossed step by step, beginning at the lowest contour line of elevationand progressively pressing the metal to the next succeeding contour lineuntil the highest elevation is reached. This is preferably accomplishedwith the embossing machine 'of m prior Patent No. 2,029,651, grantedFebruary 4, 1936. Such original relief map is then secured upon a rigidbacking, the back side of the elevated areas being filled withHydrostone or other suitable hardening filler for purposes ofreinforcement. A suitable frame is then secured around the original mapand a mold matrix is then cast thereon and allowed to harden.

A completed mold matrix produced as just described for making duplicatesof the original relief map is indicated at I in Figs. 1 and 4. Such moldmatrix is provided with a series of holes extending verticallytherethrough at the levels of different elevation as illustrated at H,I2, 13 and I l. The number and spacing of such holes will be determinedprimarily by the character of the contour in any given case, but ingeneral the holes will be located ever few inches and communicate withdifferent elevation levels, but in areas which are fiat a substantiallygreater spacing of the holes is satisfactory. The holes may be formedincident to casting of the mold matrix by securing small pegs to theoriginal map which are removed when the mold matrix has hardened, orthey may be formed by drilling following completion of the mold.

It will be understood that mold matrix It! is a female mold with thepoints of deepest impression therein representing the points of highestelevation of the map. Such matrix is placed in a rigid frame 15 of mynew duplicating machine. As shown in Fig. 1 such frame should be oflarger size than the matrix to leave a space between the frame and thesidewalls of the matrix. frame'is provided wth a closed bottom wall I 5and the matrix is supported in spaced relation thereto b a series ofspacer elements ll so that there is a continuous space between thematrix and both the bottom and sides of the frame. Frame 55 is supportedin horizontal position in any suitable manner, as by means of table I 8.

Communicating with the interior of frame [5 is a vacuum line I 9connecting with a vacuum source such as a pump. Also mounted on theframe and communicating with the interior are a vacuum gauge 20 and ableed valve 2|, Coactive with the upper side of frame I5 is a clampingframe 22 which can be removably secured to the main frame by a series ofbolts or other securing elements 23.

Located over the face side of mold matrix If! is a convection airheating space. As shown in Fig. 1 heating of the air may beaccomplishedby a battery of infra-red or other suitable electric The 'of mold matrix In so as to avoid hot spots at the molding surface of thematrix. A reflecting hood 26 is associated with the lamps to direct theheated air downwardly towards the mold. Preferably, but not necessarily,such hood extends downwardly to clamping frame 22 to completely closethe space over the matrix and provide a hot air chamber 21, thuspreventing the uncontrolled escape of heat and enabling the moldingoperation to be carried out in a shorter time than if an air gap is leftbetween reflector hood 26 and clamping frame 22. Observation and accessto the interior of the hood may be provided by a series of transparenthinged windows 28. To insure continuous and uniform circulationventilators are provided to permit the continuous and controlleddischarge of the air flow after passage over the mold. In the presentmachine windows 28 also serve as such air discharge ventilators, beingadjustable to an degree of opening to control temperature. Extendinginto the interior of the hood is a thermometer 29 to show the interiortemperature.

The air heated by lamps 24 is positively circulated by means of anelectric circulating fan 30. Preferably, and as shown, such fan will bemounted to circulate air vertically towards the face of matrix I 0 froma point substantially removed therefrom, thereby to insure uniformdistribution of the air over the entire area of the matrix. Inembodiment shown in Fig. 1 an air inlet conduit 3| to bring fresh air incontinually from outside is mounted on the top of hood 2B. Circulatingfan 30 is supported adjacent the upper inlet end thereof on a bracket32, and the supporting frame for the battery of lamps 24 is secured inconduit 3| below the fan. Mounted on the exterior of conduit 3|, or atany other convenient point, are rheostat 33 for varying the speed of fanand electric switch 34 for turning lamps 24 on and off.

Hood 26 and the associate parts just described are mounted for verticalmovement relative to the position of mold matrix I 0. Any suitable formof mounting may be employed. In the present case a pair ofcounterweighted cables 35 supported by ceiling-mounted pulleys 36connect with the upper end of conduit 3| so that the entire reflectorhood assembly may be easily raised and lowered. To insure properregistry of hood 26 with frame I5 and 22 the lower end of the hood maybe provided with a flange 31 adapted to seat against the upper side ofclamping frame 22 and apertured to receive and be secured by bolts 23.

In producing duplicate relief maps withthe machine and according to theprocess described a flat map blank S of Vinylite is printed or otherwiseinscribed on its top face with elevation contour lines L, elevationlegends E and any other desired symbols, also with different coloredareas if desired, all in exact accordance with the original mappreviously described. The printed map blank S is shown in Fig. 3.

The flat map blank S is then placed in the machine with its printed facedown facing the mold matrix I. Blank S should have a marginal area of atleast two inches beyond the mold surface and conform generally to thesize of frame l5. Where a series of bolts 23 are used as frame securingmeans, as shown, the blank can be made small enough to lie within thebolts so as to avoid puncturing the margins of the blank to receive thebolts.

ages-me s Accurate registry-pf the contour lines of map blankiS' withthe corresponding contour portionsof the" mold matrix is essential.-'.Tliis can be ac=- complished easily where-blank 'S is of transparentmateniali- When the blank is opaque an' identicalltransparerit' fiat mapblank canfir'st'be -1'egis-' tere'd with the matrixand a plurality ofpin holes 1 punched' therethrough into the 'topof frame t5, 1 1following which the transparent*blankfiis "re-" moved andregistered-withthe opaque blank-S. '10 Corresponding pin holes will be'punched throughbIan-k S and the blank-thenplaced on the frame over the matrix with"the" pin holes therein regis'i tering with those in the frame;Obviously other expedients can be employed-for registering pur 5 poses.r

With themap blank registered with the mo'ld matrixbla'mpingframe22"isplaced on the bIafhk margi'njfihe hood 26' "lowered= and bolts 23"insertedthrough frame 22 and into frame was firmly clampthe' margins ofthe mapblan'k with sealing engagement. "During this installing operationvacuum bleed valve Zls'hould'be entirlY openor the source of "vacuumsupplied through line l9 should be cut off. When installationhas 25 beencompleted vacuum is supplied to the interi'or of frame' lethroughlirielfig" Since the vacuum? initially employed -wilbbe less-thanthat supplied; va1ve"-"2l wilhfirs't "beentirely openg 'and thenzclosedslightly to'supply-a low-'vacuum of about one inchf By reason'of thefact that-the vacuumis sup plied to the" space between the sides" of*matri-x i m ain'd 'frame I'5 the margins-of map blank S are drawn--into 'lightengagement with the" top mar= gins' of the mold inwardlyadjacent the'edgs of the mold This has been found *oiuite important inpreventing subsequent formation'of wrinkles in the'marginal portions ofthe map-blank which engagesuc htop margins'of the mold during *the'" 4actual molding-"operation; When vacuum is suppliedat this' time tothefac'e of the-blank opposedto the mold matrix a slight deformation ofthe-"=- blank" into the 'mold' cavities frequently is ob tained-i 1Switch 34 turned on to energize'the heatirig lamps 24 "and 'rhe'ostat33*i's turnedup partiall'y to operate circulating fan '30 at onlymoderate speed. One or'more of hinged windows-28"i"n hood-' 26 should'be' open so 'thatfres'h"air'=drawn in" through "conduit '3 l i's heatedby the' lamps 24: circulated through ho'od 2'6 over the'iac'e of sheet san'd 'allowe'd' to escape" through open"windows 2B. In this manner thetemperatureof the'sheet is raisedgradually' up'to and beyond its'softe'ning point: As the temperature rises 'vac'uum "bleed' valve z I'moved in intermitte'nt stages towards closed'position to increase thevacuum acting o'n the 'opposite' sid 0f the sheet through'the' holes jin mold matrix It. Thetemperatureofthsheet" and the" amount of vacuumcan be watched through'thermometer'ZB'and gauge zllf tem V perature ofthe sheet canberaisedfasterbrmore slowly" by regulating rheostat' 33" toad'jiistfthe speed of the fan and the degree of vacuum lcanbe preciselyregulated by adjustmentf'bfbleed valve 2|? As previo isly "pointed out apreliminary jlowvacuum is applied: to the sheet before 'softe ningcommences; It is extremelyundesirabl e to heat the sheet preliminaryto'beingclamped in posi' tion' and drawn into engagement"withthe'mold byth'ewacuum." Asalrady" further pointed out molding'of areas of-mapblanks oflow-elevation is carried out after the blank has been raisdto''lfi' a temperature shortof its 'sortening 'pomt'butat which under thevacuum it can =be drawn into con-" tact with 'shallower" mold surfaceareas :1 orthemoldiand each successive area- 0f higher elevation ismolded 'successively into contact with deeper mold surfaceareas-as thetemperature of a; sheet is brought up to and=beyond its softening pointby increasing the degree of vacuum in stages?" In this manner an area oflower elevation of map blank fS is expanded-into the corresponding partof the:mold-landiseatedragainst further expansion before'san adjoiningarea of higher elevation :is 5 expanded: Areas of maximum elevation willbe thelast molded, maximum temperature and'vace uum being 'emp'loyedf orthis' purpose. All of this will be 'under'stood by reference to Fig. 4.V Thefnumber 'o'i stages in which the-vacuum is increased; likeWiSe the'amount of =increase'in re=- lationito the rising temperature of thesheet, *wil i be varied-i-depending upon the character of the relief: Arelief whi'ch has :only small difff'ences' in elevation between theminimum and-maximum can-be completely molded in fewer stages andwithless'vacuum'end temperature and in less timethan a reliefwhicli hassubstantialdifferences in elevation. 7

After map blank S has 1 been completely molded' switched 'is operated toturn ofi'lamps 24.-

Rhee

stat 33 is turned on full to cause fan 3fi'torapidly circulate incomingcool air through hood =26 'ver moldin'gsheet S. Atthi's time hingedwin'dows 28 should befully'o-pen.- Tl'i'evacuum is con tinued as sheet Sgradually cool's below its 'soften'=--- I ing point and sets. Cooling iscontinued a t--1east= down to "F. and can becarrieddoWn to roomtemperature." When 'cooiin'g hasbeen completed bleed'valve 2l' wi11beopen fully'to'eliminatethe vacuum,ibolts;2.3 will be withdrawn, hood' 26an'd clampingrring: 22 raised and thecompletedrelief map sheet Swithdrawn from mold matrix HI. A new'sheet is the'n'placed in theapparatusandthe entire process repeated until 1 the desired riumbei ofduplicatefrelieffmaps have been obtained. Of course mold matrix it maybe removedfrom the vacuum chamber and replaced by anew matrix at anytime;

The process herein described'will produce'relif naps with'grea taccuracy and 'withelevation lines and other indicia exactly in theirproper locatlom and this even though comparatively high eIeVationsarepresent. Inasmuch as relief mapsre quired forordinary purposes areon' a compara' tively small scale the maximum relief to be molded inlthesheet will not exceed one or two inches. However, the process has beenfound adaptable to successful molding to'amplitudes oi five inchesandmore provided the processcbejcarm riedyout by raising the temperatureand vacuum very gradually." i a The invention has been described in itsiapplij cation tothe duplication of relief maps, to em-. phasize itsadaptability to precision work. It will be understood; however, that theinvention .is equally adaptable to'rnolding other types of relief.. .7in thermoplastic sheet material, either utilitarian -l or purelyornamental.

The term of the apparatus herein illustrated; and described and thesuggested'ranges :of item-W perature and pressure are to be'taken asonly] exemplary, all being subject to "considerable Ivaria= tionrdepending upon the .nature oftthe the'rmm plastic sheet material" usedand thelcharactertoio the relief to beprodu'ced. The scope of.theinvention "isto" be determined by thesappendedal claims.

in molding position across the open side thereof,

a hooded reflector and hot air heating means over- I lying the open faceof the box coactive to uniformly heat the entire area of a blank whensecured to the box, and means for supplying a varying blank moldingvacuum interiorally of the box.

2. A relief duplicating machine comprising a vacuum box having an openside and adapted to support a mold matrix adjacent said open side, meansfor removably securing a blank sheet to be molded in sealing engagementwith the box in molding position across the open side thereof, a hoodoverlying the open side of the box and defining an air chamber, airheating means mounted in said hood, circulating means for circulatingair over the heating means and for causin heated air to flow over ablank when in molding position, and means communicating with theinterior of the box for supplying a varying vacuum to the mold side of ablank when in molding position.

3. A relief duplicating machine comprising a vacuum box having an openside and adapted to support a mold matrix adjacent said open side,

means for removably securing a blank sheet to be molded in sealingengagement with the box in molding position across the open sidethereof, a hood overlying the open side of the box and defining an airchamber, air heating means mounted in said hood, air inlet means foradmittin fresh air into the hood, a fan for drawing air into the hoodthrough said air inlet means and for circulating air over the heatingmeans and over a blank when in moldin position, and means communicatingwith the interior of the box for supplying a varying vacuum to the moldside of a blank when in molding position.

4. A relief duplicating machine comprising a vacuum box having an openside and adapted to support a mold matrix adjacent said open side, meansfor removably securing a blank sheet 'to be molded in sealing engagementwith the box in molding position across the open side thereof, a closedhood overlyin the open side of the box, means mounting the hood forvertical movement away from the box to permit insertion and 1emoval ofblanks, an air inlet in the hood, air heating means and air circulatingmeans mounted in the hood, and air outlet means in the hood, and meanscommunicatin with the interior of the box for supplying a varying vacuumto the mold side of a blank when in molding position.

5. A relief duplicating machine comprising a vacuum box having an openside and adapted to support a mold matrix adjacent said open side, meansfor removably securing a blank sheet to be molded in sealing engagementwith the box in molding position across the open side thereof, variablespeed air circulatin means mounted outwardly of the open side of the boxadapted to circulate air over a blank when in molding position, meansfor heating the air to be circulated regulating means for varying thespeed of the circulating means adapted to control and vary thetemperature of a blank when in molding position, and means communicatingwith the interior of thebox for supplying a varying vacuum to the moldside of a blank when in molding position.

6. A-relief duplicating machine comprising a relief mold matrix havingrecurrent ports extending therethrough and communicatin 'with themolding surface, a vacuum box having an open side in which the moldmatrix is mounted with its molding surface adjacent said open side,means for removably securing a moldable blank of greater size than themold to the box in moldin p sition across the open side 'of the box,'the

box being of greater internal dimensions than the mold matrix so as toprovide a closed vacuum space around the mold for supplying vacuumthrough the mold matrix ports to the underside of the area of a moldableblank overlying the mold matrix and also to supply vacuum to themarginal areas of a moldable blank beyond the mold matrix when such amoldable blank is in molding position, means for supplying vacuum to theinterior of the box; means for regulating the amount of vacuum in thebox, and means for heating a blank when in molding position and whilesubject to vacuum.

'7. In a relief duplicating machine, a vacuum 'box having an open sideand adapted to removably support a mold matrix therein. with the moldingsurface of the mold facing said open side, means for removably securinga blank sheet to be molded in sealing engagement with the box in moldingposition across the open side thereof,

means for heating the exposed face of the blank,

an inlet port in the box'for supplying molding vacuum to the boxinterior, a vent port in the .box and'an adjustable molding vacuumregulating vent valve connecting with said vent port providingcommunication between the interior 1 of the box and the atmosphereoperable during molding tocontrol and varying-the degree of vacuum inthe box.

8. A method of producing relief having local areas of differentelevation in a blank of thermoplastic sheet material through vacuum andheat which comprises'supporting the blank in the hard state against'theoutermost face surfaces of a female relief mold having multiple localmolding surface areas of different depth and with the margins of theblank rigidly secured, uniformly heating the side of the blank away fromthe mold so as'to gradually raise the temperature of the blank andapplying vacuum to the mold side of the blank, beginning while the blankis still below its softening point, and as the temperature of the blankrises progressively increasingthe vac- ,uum in controlled amount on themold side of the blank so as to draw the blank into contact with thelocal molding surface areas of different depth progressively, startingwith molding surface areas of lesser depth. r

9. A method of producing relief according to claim 8, wherein theapplied vacuum is progressively increased in controlled amount inintermittent stages.

10. A method ofproducing relief having local areas of differentelevation in a blank of thermoplastic sheet material through vacuum andheat which comprises supporting the blank in the hard state against theoutermost face surfaces of a V female relief mold having multiple localmolding surface areas of different depth and with the margins of theblank rigidly secured, applying a preliminary 0w vacuumto the mold sideof the blank while still in the hard state only suflicient to draw theblank against the outermost face surfaces of themold, uniformly heatingthe side of the blank away from the mold so as to gradually raise thetemperatureof the blank and as lesser depth.

starting wit depth.

cei ri if I the temperature cf the blank rises progressivelyincreasing-and controlling-the amount'of vacyy-uumso as to draw the w 7the localmolding surface 'a reas of different depth .blankinto: contactwith progressively, starting with molding areas of 11; method ofproducing relief having local ;areas of different elevaticn in-a blankof thermoplastic sheet material which comprises supporting the blank inthe hard stateagainst theoutermost face surfaces of a female =relif moldhaving multiple-local molding surface areas of different depth an'd withthe margins of the blank extending beyond; the; sides pf the mold-and"yrigidly secured inoutward spaced relation to the sides of the mold;applying heat to the side of the blank away from the mold so as togradually -raise thetemperature Y 'i'temperaturerises applying vacuum inprogressively increased control-led amount to the moldv of the blank andas the side of the blank so as to draw the blank "into contact with thelocal molding; surface areas of "different depth progressively, startingwith molding surface areas-of lesser depth, andthroughout f the blankmoldingoperation holding the rigidly secured margins of the'blankbeyondthe mold by applying vacuum to the moldside of said'margins.

- 12. Arnethodof producingrelief having local "areas of differentelevation in a blank of "thermos.

plastic sheet material, through vacuum and 'heat which comprisessupporting the blank against the outermost-face surfaces of a femalerelif mold having multi'ple l ocal molding surfaces of'different depthand with the rigidly secured, heating the blank by'fcoritinuouslycirculating a hot dry 'ga's' atsubstantially atmospheric pressureuniformly over""th'e""'side ,Of'the blank away from the nioldsd stofg'radually raise the temperature of 'the bl'arili and as thetemperature of theblank rises applying a -vacuum in progressivelyincreased" controlled amount to the mol'dside of the-blank so as' tomold the blank into contact with -thelocal'iriolding surface areas ofdifferent depth progressively,

' 'the mold ing surface areas of lesser '13. A- rnethod1of producing"reliefhaving' local areasof different elevation in a blank ofthermoplastic sheet material thr lugli vacuum heat whichcomprises-supporting the Blank in the hard state against theoutermostfaceflsurfaces of a I female relief mold having multiple localmold- 'ing-surfaceareas of difierent depth and with the margins of theblankrig-idlysecured-apply,

' ing a preliminary low vacuum to the mold side of the blank, thencirculating a hot dry gas'uniformly over the opposite side of the blankso as to gradually raise the temperature of the blank and as thetemperature rises progressively increasing and controlling the amount ofvacuum so as to mold theblank into contact 'with thelocal moldingsurface areas ofdififerent"depth progresslvely, starting with themoldingsurface areas of lesser-depth.

14. A method of prbaucing rner having local argins or th''blank sideboth at-the margins-and throughout the liminary low vacuum to the blankfrom th mold entire mold area, then circulatin a hot-dry gas uniformlyover the opposite side of the blank so as to gradually raise thetemperature o'f the blank and as the temperature ofthe-blank-risesprogressively increasing and controllinglthe amount of vacuum so as tomoldtheblank'into contact with the local moldin surfaces'of differentdepth progressively, startingwitli -the molding surface areas of lesserdepth. 7

15. A method of producing reliefin ablank of the thermoplastiesheetmaterial through? vacuum and heat which comprises supporting the blankin the hard state against the outermost f face surfaces of a femalerelief mold arid with, the margins of-the blank rigidly secured,applying a preliminary low vacuum to the mold side of the blank whilestill in the hard state, heatin lthe side of the blank away from themold and as the temperature of the blank rises increasingand controllingthe amount of vacuum so as to draw the blank into contact with themolding surfaces of the mold.

16. A method of producing relief in a blank of thermoplastic sheetmaterial through vacuum and heat which comprises supporting the blank inthe hard state against the outermost face surfaces of a female reliefmold and with the 'margins of the blank extending beyondthe sides of themold and rigidly secured in outward spaced relation to the sides of themoliapplyingla preliminary low vacuum to the mold side of the I blanksimultaneously at the margins andthroughout the entire mold area whilethe'blank is' still in the hard state, heating the side of the-blankaway from the mold and as the temperature of the'blank rises applying ahigher vacuum to the "mold side of 'theblank so as to draw the blankinto contact with moldin surfaces of the mold. 1'7. In the method ofproducing relief in-a-blank of thermoplastic sheet material, the stepsof-supi porting the blank against the marginal face surfaces of a reliefmold with the margins of the 'blankextending beyond the sides of themold and rigidly secured in outward spaced relation to the sides of themold, molding the blank to the-contour of the mold,and-throughoutmolding holding'the'rigidly secured margins of the blankbeyond the sides of the mold by: applyingvacuum to'the mold side ofsaidirigidly secured margins. 18. A method of producing relief inablankof thermoplastic sheet material through vacuum and heat which comprisessupporting the blank in the hard state against'the outermostfacesurfaces of-a female reliefmold and with the margins of theblankextending-beyond thesides of the mold and rigidly secured in outwardspaced relation to the sides of the' mold, applyingapreliminary lowvacuum to themoldside of the margins of the blank, while the blan-k isstill in the hard state; heating:thelopposite side of the-blank and asthe temperature of thesbl-ank rises applying ahigher vacuum to themold--side tact with molding surfaces of themold.

19. Amethod of producing-relief in-ablank of thermoplastic sheet,material jthrough-- vacuum relief mold and withthe marginsof:-the-blank -=rigid1y secured, heating theblank by continuand heatwhich comprises supportingthe-blank against theoutermost face surfacesof a female ously circulating hot'dry-gas at substantially at- 'mospherepressure, overtheside of-th+b1ank away from-the-mold so as to raise thetemperature of the blank uniformly over the entire mold andsimultaneously applying a controlled vacuum to the mold side of theblank to draw the blank underheating into contact with molding surfacesof the mold.

20. A method of producing relief in a blank of thermoplastic sheetmaterial through vacuum and heat which comprises supporting the blankagainst the outermost face surfaces of a female relief mold and with themargins of the blank rigidly secured, heating the blank by flowing acontinuously replenished stream of hot air over the side of the blankaway from the mold to gradually raise the temperature of the blank,continuousl'y removing at least a portion of the hot air after flowingover the blank and applying vacuum to the mold side of the heated blankto draw the blank into contact with the molding surfaces of the mold.

21. A method of producing an article having relief and containingcorrelated visible indicia in accurate registry with the relief whichcomprises supporting a blank of thermoplastic sheet material inscribedwith the correlated indicia and in hard state against the outermostface, surfaces of a female relief mold with the indicia of the blank inaccurate registry with corresponding points of the relief of the moldand with the margins of the blank rigidly secured, uniformly heating theside of the inscribed blank away from the mold so as to gradually raisethe temperature of the blank and applying vacuum to the mold side of theblank, beginning while the blank is below its softening point, and asthe temperature of the blank rises progressively increasing the vacuumin controlled amount on the mold side of the blank so as to draw theblank into contact with the relief molding surfaces of the mold ofdifferent depth progressively, starting with the molding surfaces oflesser depth, and maintain accurate registry of the correlated indiciawith corresponding points of relief of the mold.

22. A method of producing an article having relief according to claim 21wherein hot air is circulated over the side of the blank away from themold to uniformly heat and gradually raise the temperature of the blank.

23. A method of duplicating a topographical relief map which comprisessupporting a map blank of thermoplastic sheet material inscribed withtopographical indicia of the desired map and in hard state against theoutermost face surfaces of a female relief mold having the relief of thedesired map with the topographical indicia in accurate registry withcorresponding points of the mold relief and with the margins of theblank rigidly secured, uniformly heatin the side of the blank away fromthe mold so as to gradually raise the temperature of the blank andapplying vacuum to the mold side of the blank, beginning while the blankis below its softening point, and as the temperature of the blank risesprogressively increasing the vacuum controlled amount on the mold sideof the blank so as to draw the blank into contact with the reliefmolding surfaces of the mold of different depth progressively, startingwith the molding surfaces of lesser depth, and maintain accurateregistry of the topographical indicia with corresponding points of therelief of the mold.

24. A method of duplicating a topographical relief map according toclaim 23, wherein hot air is circulated over the side of the map blankaway from the mold to uniformly heat and gradually raise the temperatureof the blank.

25. A relief map duplicating machine comprising a vacuum box having anopen side and adapted to support a mold matrix therein adjacent saidopen side, means for removably securing a blank sheet to be molded insealin engagement with the box in molding position across the open sidethereof, regulatable means communicating with the atmosphere forcontinuously flowing a controlled and varying amount of hot air atsubstantially atmospheric pressure uniformly on the outer face of theblank when in molding position, and means communicating with theinterior of the box regulatable to supply a varying vacuum to the moldside of a blank during heating in molding position to draw the blankinto the mold.

26. A relief duplicating machine comprising a vacuum box having an openside and adapted to support a mold matrix adjacent said open side, meansfor removably securing a blank sheet to be molded in sealing engagementwith the box in molding position across the open side thereof, meanscommunicating with the atmosphere located outwardly of the open side ofthe box operable to continuously flow hot dry fluid at substantiallyatmospheric pressure uniformly on the outer face of the blank when inmolding position, and means communicating with the interior of the boxfor supplying a varying vacuum to the mold side of a blank duringheating in molding position to draw the blank into the mold.

JOHN J. BRAUND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 130,140 Judson Aug. 6, 1872597,929 Burns et al. Jan. 25, 1898 1,387,805 Roberts Aug. 16, 19211,737,874 Busch Dec. 3, 1929 2,345,112 Grundel Mar. 28, 1944 2,377,946Leary June 12, 1945

